Apparatus for positioning a treating liquid at the bottom of a well

Abstract

This invention relates to a method and apparatus for positioning a selected liquid at the bottom of a well, such as an oil well, while having in the well at least a string of tubing, a sucker rod pump, a string of sucker rods, and a standing valve, without disturbing the rods, pump, tubing, or standing valve. A bypass conduit or shroud surrounds the wall of the tubing at a point above the pump where there is an opening in the wall of the tubing and is carried down, outside the tubing to a point below the conventional mud anchor, into the inlet of an overpressure relief valve. The outlet of the valve empties into the well annulus. If the normal pressure at the bottom of the tubing due to the head of liquid in the tubing is P, the overpressure valve is set to open at a pressure of P+P1, where P1 is a selected value, such as say 100 psi. At the surface, means are provided to close off the top of the tubing. Means are provided to inject the selected liquid into the top of the tubing at a selected pressure P2 above atmospheric, where P2 may be say 150 psi. This causes the pressure at the bottom of the tubing to rise to P+P2. Since P+P2 is now greater than P+P1, the overpressure valve will open and pass as much liquid as is pumped into the tubing at the surface. A crossflow unit is inserted into the tubing and the shroud at the standing valve to permit the radial flow of well fluids from outside the shroud to the inlet to the standing valve, and to permit the longitudinal flow of liquid down the annulus inside the shroud, to the relief valve.

What is claimed is: 
     
       1. In a liquid producing well having installed at least a string of tubing extending from the surface to the bottom, a standing valve, a sucker rod pump including a traveling valve, and a string of sucker rods, apparatus for positioning a selected volume of a selected fluid in the bottom of said well without disturbing said pump, rods, tubing, or standing valve, comprising; (a) a first opening in said tubing above said sucker rod pump;   (b) a shroud, or cylindrical pipe, outside of, said tubing string, forming an annulus between said tubing and said shroud, said shroud extending to a point below the inlet to said sucker rod pump, from a point above said first opening; means to seal said shroud to the outside of said tubing string above said first opening;   (c) crossover means inserted into said tubing string in the vicinity of the inlet to said sucker rod pump; said crossover means sealed to said shroud; permitting radial flow of well fluid from outside said shroud to the inlet to said sucker rod pump, and also permitting longitudinal flow of fluid down said annulus from said first opening to the bottom of said shroud;   (d) an overpressure relief valve set to open at a selected fluid pressure on its inlet, said relief valve positioned at and closing off the bottom end of said shroud;   (e) at the mouth of said well, means to close off the top of said tubing string; and   (f) means to inject at least a selected first volume of a selected first fluid, into said closed top end of said tubing at a selected pressure above atmospheric pressure.   
     
     
       2. The apparatus as in claim 1 in which said means to seal said shroud to the outside of said tubing string comprises expandable packer means. 
     
     
       3. The apparatus as in claim 2 in which said expandable packer means comprises; (a) a thin-walled cylinder, or shell, and means to attach said shell to the top of said shroud;   (b) elastomeric ring means adapted to be slipped over said tubing, and shelf means in said shell for supporting, from the bottom, said elastomeric ring means;   (c) tubular cylindrical packing nut means adapted to be slipped over said tubing, and having threads on the outer surface matching threads on the inner wall of said shell;   whereby when said packing nut is screwed down in said shell it compresses said elastomeric ring means causing it to expand radially inwardly, and seal against the outer wall of said tubing.   
     
     
       4. The apparatus as in claim 3 including metal ring means above and below said elastomeric ring means, to transfer to said elastomeric ring means the compressive force provided by said shelf means and said packing nut means. 
     
     
       5. The apparatus as in claim 1 in which said crossover means comprises (a) a metallic cylindrical ring of selected concentric inner and outer diameter and height;   (b) at least one radial opening through the cylindrical wall of said ring near the longitudinal center thereof;   (c) at least one longitudinal opening through the wall of said ring;   (d) first means to attach and seal said tubing to the inside of said ring extending upwardly and downwardly; and   (e) second means to attach and seal said shroud to the outside of said ring extending upwardly and downwardly.   
     
     
       6. The apparatus as in claim 5 in which said first means to attach and seal said tubing comprises internal pipe threads on the internal surface of said ring adapted to mesh with the threaded ends of said tubing. 
     
     
       7. The apparatus as in claim 5 in which said second means to attach and seal said shroud comprises; male pipe threads on the external surface of said ring adapted to mesh with the internal threads of a collar of said shroud. 
     
     
       8. The apparatus as in claim 5 in which said first means to attach and seal said tubing comprises two tubing collar means welded to the inner surface of said ring, extending out of each end of said ring. 
     
     
       9. The apparatus as in claim 5 in which said second means to attach and seal said shroud comprises two shroud collar means welded to the outer surface of said ring, extending out of each end of said ring. 
     
     
       10. The apparatus as in claim 1 including spring centralizer means mounted on the bottom end of said shroud means; whereby when said sucker rod pump is operating, and the bottom end of said tubing and shroud will rise and fall in synchronism with said pump strokes, and said centralizer will scrape the wall of said borehole.   
     
     
       11. The apparatus as in claim 1 including means to inject a second selected volume of a second selected fluid into said closed end of said tubing at a selected pressure above atmospheric pressure.